diff --git a/CHANGELOG.md b/CHANGELOG.md
index f905bfa..f7b6363 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,18 @@ All notable changes to SuperBased Observer are documented here.
 
 ## [Unreleased]
 
+### Changed
+
+- **perf(cost): push historical noise filtering into SQLite** — cost
+  summaries now exclude synthetic-model and all-zero token rows in the source
+  queries before Go allocates raw rows or runs per-turn rollups. The Go-side
+  noise guard remains as a defensive backstop.
+- **perf(db): gate low-value `observer db vacuum` rebuilds** — the CLI and
+  dashboard vacuum path now checks reclaimable free pages first, skips the
+  full-file rebuild below `max(64 MiB, 2% of DB size)`, bounds the rebuild
+  with a 10-minute context timeout, and exposes `--force` for explicit
+  operator compaction.
+
 ## [1.32.0] — 2026-08-26
 
 ### Fixed
@@ -2982,6 +2994,7 @@ All notable changes to SuperBased Observer are documented here.
 - **Contact email domain migrated `marmut.app` → `superbased.app`** across
   documentation, package metadata, and the website source.
 
+
 ## [1.8.4] — 2026-06-12
 
 ### Changed
diff --git a/README.md b/README.md
index 8701aae..df5e937 100644
--- a/README.md
+++ b/README.md
@@ -1056,7 +1056,7 @@ lint-gated policy editor, budget guardrails, evidence downloads) — see the
 | `observer contract [--json]` | The published stability contract: every MCP tool with its tier (stable / conditional / experimental) plus each adapter's public capability row. `--json` emits the `contract_version`-stamped artifact an integrator pins. Prose: [`docs/mcp-contract.md`](docs/mcp-contract.md). |
 | `observer adapters [--json]` | The full adapter capability matrix (proxy / surface / hook / MCP / native / token / handoff / attach / resume), generated from the capability registry. |
 | `observer prune` | Run retention now. |
-| `observer db stats\|vacuum\|backup` | Storage manager: per-table size breakdown (index + FTS5 shadow bytes folded in), reclaim free pages with bytes-freed report, online snapshot via `VACUUM INTO` (safe while the daemon runs; refuses overwrite). |
+| `observer db stats\|vacuum\|backup` | Storage manager: per-table size breakdown (index + FTS5 shadow bytes folded in), reclaim free pages with bytes-freed report, online snapshot via `VACUUM INTO` (safe while the daemon runs; refuses overwrite). `db vacuum` skips the full rebuild when reclaimable space is below `max(64 MiB, 2% of DB size)`; pass `--force` to compact anyway. |
 | `observer db import <path> [--dry-run]` | Merge another `observer.db` (a stranded install from another OS / home dir) into this node's. Idempotent single-transaction merge; `--dry-run` rolls the same transaction back for exact counts. Migrates the source first — point it at a copy. |
 | `observer metrics [--port N]` | Prometheus `/metrics` endpoint. |
 | `observer export {json\|csv\|xlsx}` | Dump tables for external analysis. |
diff --git a/cmd/observer/dbcmd.go b/cmd/observer/dbcmd.go
index 7a2522d..06a01e2 100644
--- a/cmd/observer/dbcmd.go
+++ b/cmd/observer/dbcmd.go
@@ -70,7 +70,10 @@ func newDBStatsCmd() *cobra.Command {
 }
 
 func newDBVacuumCmd() *cobra.Command {
-	var configPath string
+	var (
+		configPath string
+		force      bool
+	)
 	cmd := &cobra.Command{
 		Use:   "vacuum",
 		Short: "Rebuild the database file to reclaim free pages (needs the write lock; pick a quiet moment)",
@@ -80,19 +83,40 @@ func newDBVacuumCmd() *cobra.Command {
 				return err
 			}
 			defer cleanup()
-			fmt.Fprintln(cmd.OutOrStdout(), "vacuum: rebuilding — this can take a while on large databases…")
-			freed, err := db.Vacuum(cmd.Context(), database)
+			opts := db.VacuumOptions{
+				MinReclaimableBytes: defaultVacuumMinReclaimableBytes,
+				MinReclaimableRatio: defaultVacuumMinReclaimableRatio,
+				Timeout:             defaultVacuumTimeout,
+			}
+			if force {
+				opts.MinReclaimableBytes = 0
+				opts.MinReclaimableRatio = 0
+			}
+			fmt.Fprintln(cmd.OutOrStdout(), "vacuum: checking reclaimable free pages…")
+			res, err := db.VacuumWithOptions(cmd.Context(), database, opts)
 			if err != nil {
 				return err
 			}
-			fmt.Fprintf(cmd.OutOrStdout(), "vacuum complete: %s reclaimed\n", fmtBytesIEC(freed))
+			if !res.Ran {
+				fmt.Fprintf(cmd.OutOrStdout(), "vacuum skipped: %s reclaimable is below the %s threshold for this %s database (use --force to run anyway)\n",
+					fmtBytesIEC(res.ReclaimableBytes), fmtBytesIEC(res.RequiredBytes), fmtBytesIEC(res.TotalBytes))
+				return nil
+			}
+			fmt.Fprintf(cmd.OutOrStdout(), "vacuum complete: %s reclaimed\n", fmtBytesIEC(res.FreedBytes))
 			return nil
 		},
 	}
 	cmd.Flags().StringVar(&configPath, "config", "", "Path to config.toml")
+	cmd.Flags().BoolVar(&force, "force", false, "Run VACUUM even when reclaimable free pages are below the default threshold")
 	return cmd
 }
 
+const (
+	defaultVacuumMinReclaimableBytes int64 = 64 << 20
+	defaultVacuumMinReclaimableRatio       = 0.02
+	defaultVacuumTimeout                   = 10 * time.Minute
+)
+
 func newDBBackupCmd() *cobra.Command {
 	var (
 		configPath string
diff --git a/internal/db/storage.go b/internal/db/storage.go
index 84f73b0..3c1f5b9 100644
--- a/internal/db/storage.go
+++ b/internal/db/storage.go
@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
+	"time"
 )
 
 // Storage manager primitives (usability arc P6.8). This file is the
@@ -161,22 +162,90 @@ func resolveOwner(name string, owners map[string]string, ftsTables []string) str
 	return name
 }
 
+// VacuumOptions controls the guarded VACUUM path.
+type VacuumOptions struct {
+	// MinReclaimableBytes skips the rebuild when the freelist is smaller
+	// than this threshold. Zero always runs.
+	MinReclaimableBytes int64
+	// MinReclaimableRatio skips the rebuild when reclaimable bytes are less
+	// than this fraction of the current DB size. Zero disables the ratio gate.
+	MinReclaimableRatio float64
+	// Timeout bounds the rebuild. Zero leaves the caller's context as-is.
+	Timeout time.Duration
+}
+
+// VacuumResult reports whether VACUUM ran and how many bytes it reclaimed.
+type VacuumResult struct {
+	Ran              bool
+	FreedBytes       int64
+	ReclaimableBytes int64
+	TotalBytes       int64
+	RequiredBytes    int64
+}
+
 // Vacuum rebuilds the database file, returning the freed bytes
 // (before − after, from page accounting). VACUUM needs the write lock
 // and temporarily doubles disk usage; run it at a quiet moment.
 func Vacuum(ctx context.Context, database *sql.DB) (freedBytes int64, err error) {
-	before, err := fileBytes(ctx, database)
+	res, err := VacuumWithOptions(ctx, database, VacuumOptions{})
 	if err != nil {
 		return 0, err
 	}
+	return res.FreedBytes, nil
+}
+
+// VacuumWithOptions is Vacuum plus an optional reclaimable-byte gate and
+// timeout. It lets automatic/UI-triggered maintenance avoid a full-file
+// rebuild when SQLite has little or nothing to reclaim, while preserving the
+// old unconditional behavior when options are zero.
+func VacuumWithOptions(ctx context.Context, database *sql.DB, opts VacuumOptions) (VacuumResult, error) {
+	if opts.Timeout > 0 {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithTimeout(ctx, opts.Timeout)
+		defer cancel()
+	}
+	reclaimable, err := reclaimableBytes(ctx, database)
+	if err != nil {
+		return VacuumResult{}, err
+	}
+	total, err := fileBytes(ctx, database)
+	if err != nil {
+		return VacuumResult{}, err
+	}
+	required := vacuumRequiredBytes(total, opts)
+	if required > 0 && reclaimable < required {
+		return VacuumResult{
+			Ran:              false,
+			ReclaimableBytes: reclaimable,
+			TotalBytes:       total,
+			RequiredBytes:    required,
+		}, nil
+	}
 	if _, err := database.ExecContext(ctx, "VACUUM"); err != nil {
-		return 0, fmt.Errorf("db.Vacuum: %w", err)
+		return VacuumResult{}, fmt.Errorf("db.Vacuum: %w", err)
 	}
 	after, err := fileBytes(ctx, database)
 	if err != nil {
-		return 0, err
+		return VacuumResult{}, err
+	}
+	return VacuumResult{
+		Ran:              true,
+		FreedBytes:       total - after,
+		ReclaimableBytes: reclaimable,
+		TotalBytes:       total,
+		RequiredBytes:    required,
+	}, nil
+}
+
+func vacuumRequiredBytes(total int64, opts VacuumOptions) int64 {
+	required := opts.MinReclaimableBytes
+	if opts.MinReclaimableRatio > 0 && total > 0 {
+		ratioRequired := int64(float64(total) * opts.MinReclaimableRatio)
+		if ratioRequired > required {
+			required = ratioRequired
+		}
 	}
-	return before - after, nil
+	return required
 }
 
 // BackupInto writes a consistent snapshot of the live database to
@@ -209,3 +278,14 @@ func fileBytes(ctx context.Context, database *sql.DB) (int64, error) {
 	}
 	return pageSize * pageCount, nil
 }
+
+func reclaimableBytes(ctx context.Context, database *sql.DB) (int64, error) {
+	var pageSize, freelist int64
+	if err := database.QueryRowContext(ctx, "PRAGMA page_size").Scan(&pageSize); err != nil {
+		return 0, fmt.Errorf("db: page_size: %w", err)
+	}
+	if err := database.QueryRowContext(ctx, "PRAGMA freelist_count").Scan(&freelist); err != nil {
+		return 0, fmt.Errorf("db: freelist_count: %w", err)
+	}
+	return pageSize * freelist, nil
+}
diff --git a/internal/db/storage_test.go b/internal/db/storage_test.go
index 2700b05..ff65ac4 100644
--- a/internal/db/storage_test.go
+++ b/internal/db/storage_test.go
@@ -137,3 +137,42 @@ func TestVacuumAndBackupInto(t *testing.T) {
 		t.Errorf("freed = %d, want >= -%d (one page of VACUUM rounding)", freed, sqlitePageSize)
 	}
 }
+
+func TestVacuumWithOptionsSkipsBelowReclaimableThreshold(t *testing.T) {
+	ctx := context.Background()
+	database, err := Open(ctx, Options{Path: filepath.Join(t.TempDir(), "s.db")})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer database.Close()
+
+	res, err := VacuumWithOptions(ctx, database, VacuumOptions{MinReclaimableBytes: 1 << 30})
+	if err != nil {
+		t.Fatalf("VacuumWithOptions: %v", err)
+	}
+	if res.Ran {
+		t.Fatal("VacuumWithOptions ran despite reclaimable bytes being below threshold")
+	}
+	if res.ReclaimableBytes >= 1<<30 {
+		t.Fatalf("test database unexpectedly has %d reclaimable bytes", res.ReclaimableBytes)
+	}
+	if res.FreedBytes != 0 {
+		t.Errorf("skipped vacuum freed bytes = %d, want 0", res.FreedBytes)
+	}
+}
+
+func TestVacuumRequiredBytesUsesLargerOfAbsoluteAndRatioThresholds(t *testing.T) {
+	opts := VacuumOptions{
+		MinReclaimableBytes: 64 << 20,
+		MinReclaimableRatio: 0.02,
+	}
+	if got, want := vacuumRequiredBytes(1<<30, opts), int64(64<<20); got != want {
+		t.Errorf("small DB threshold = %d, want %d", got, want)
+	}
+	if got, want := vacuumRequiredBytes(40<<30, opts), int64(858993459); got != want {
+		t.Errorf("40 GiB DB threshold = %d, want %d", got, want)
+	}
+	if got := vacuumRequiredBytes(40<<30, VacuumOptions{}); got != 0 {
+		t.Errorf("force/zero gate threshold = %d, want 0", got)
+	}
+}
diff --git a/internal/intelligence/cost/summary.go b/internal/intelligence/cost/summary.go
index 1268a22..80882ad 100644
--- a/internal/intelligence/cost/summary.go
+++ b/internal/intelligence/cost/summary.go
@@ -729,6 +729,7 @@ func (e *Engine) loadProxyRows(ctx context.Context, db *sql.DB, opts Options, si
 		where = append(where, "at.timestamp >= ?")
 		args = append(args, since.UTC().Format(time.RFC3339Nano))
 	}
+	where = append(where, proxyNoiseWhere("at"))
 	if !opts.Until.IsZero() {
 		where = append(where, "at.timestamp < ?")
 		args = append(args, opts.Until.UTC().Format(time.RFC3339Nano))
@@ -815,6 +816,7 @@ func (e *Engine) loadJSONLRows(ctx context.Context, db *sql.DB, opts Options, si
 		where = append(where, "tu.timestamp >= ?")
 		args = append(args, since.UTC().Format(time.RFC3339Nano))
 	}
+	where = append(where, jsonlNoiseWhere("tu"))
 	if !opts.Until.IsZero() {
 		where = append(where, "tu.timestamp < ?")
 		args = append(args, opts.Until.UTC().Format(time.RFC3339Nano))
@@ -900,6 +902,7 @@ func (e *Engine) loadSummaryCallRows(ctx context.Context, db *sql.DB, opts Optio
 		where = append(where, "timestamp >= ?")
 		args = append(args, since.UTC().Format(time.RFC3339Nano))
 	}
+	where = append(where, summaryCallNoiseWhere())
 	if !opts.Until.IsZero() {
 		where = append(where, "timestamp < ?")
 		args = append(args, opts.Until.UTC().Format(time.RFC3339Nano))
@@ -953,6 +956,41 @@ func (e *Engine) loadSummaryCallRows(ctx context.Context, db *sql.DB, opts Optio
 	return out, nil
 }
 
+func proxyNoiseWhere(alias string) string {
+	return fmt.Sprintf(`COALESCE(%[1]s.model, '') != '<synthetic>' AND (
+		COALESCE(%[1]s.input_tokens, 0) != 0 OR
+		COALESCE(%[1]s.output_tokens, 0) != 0 OR
+		COALESCE(%[1]s.cache_read_tokens, 0) != 0 OR
+		COALESCE(%[1]s.cache_creation_tokens, 0) != 0 OR
+		COALESCE(%[1]s.cache_creation_1h_tokens, 0) != 0 OR
+		COALESCE(%[1]s.web_search_requests, 0) != 0 OR
+		COALESCE(%[1]s.cost_usd, 0) != 0
+	)`, alias)
+}
+
+func jsonlNoiseWhere(alias string) string {
+	return fmt.Sprintf(`COALESCE(%[1]s.model, '') != '<synthetic>' AND (
+		COALESCE(%[1]s.input_tokens, 0) != 0 OR
+		COALESCE(%[1]s.output_tokens, 0) != 0 OR
+		COALESCE(%[1]s.cache_read_tokens, 0) != 0 OR
+		COALESCE(%[1]s.cache_creation_tokens, 0) != 0 OR
+		COALESCE(%[1]s.cache_creation_1h_tokens, 0) != 0 OR
+		COALESCE(%[1]s.reasoning_tokens, 0) != 0 OR
+		COALESCE(%[1]s.web_search_requests, 0) != 0 OR
+		COALESCE(%[1]s.estimated_cost_usd, 0) != 0
+	)`, alias)
+}
+
+func summaryCallNoiseWhere() string {
+	return `COALESCE(model, '') != '<synthetic>' AND (
+		COALESCE(input_tokens, 0) != 0 OR
+		COALESCE(output_tokens, 0) != 0 OR
+		COALESCE(cache_read_tokens, 0) != 0 OR
+		COALESCE(cache_creation_tokens, 0) != 0 OR
+		COALESCE(cost_usd, 0) != 0
+	)`
+}
+
 // bucket holds the in-progress aggregation for one group key.
 type bucket struct {
 	tokens    TokenBundle